I. Field of the Invention
This invention relates to a propellant composition for aerosol dispensers which is in the form of an oil-in-water microemulsion. More particularly, this invention relates to a composition and method for rendering highly flammable gaseous aerosol propellants non-flammable by dissolving the gaseous propellants in a water-immiscible solvent which is the dispersed phase of and oil-in-water microemulsion system.
It is known from U.S. Pat. No. 3,207,386 to Presant, et al. to suppress the flammability of gaseous propellants for aerosol dispensers by dissolving the propellant in a continuous liquid aqueous phase. However, according to Presant, the maximum concentration of the flammable propellant in the aqueous phase is determined by the limit of its solubility.
On the other hand, the microemulsion technology has also been highly developed, although the primary area of application for both oil-in-water and water-in-oil microemulsions is in the petroleum industry for oil recovery processes. Microemulsions have the advantages of being thermodynamically stable and transparent or clear systems and, therefore, would readily lend themselves to commercial application for consumer and industrial products. Representative of the patent art relating to the use of microemulsions for oil and petroleum recovery include U.S. Pat. Nos. 2,356,205, 3,254,714, 3,301,325, 3,307,628, 3,536,136, 3,540,532, 3,719,606, 3,954,627 and 4,252,657. Water-in-oil microemulsion systems having utility as lubricants for diesel and gasoline engine service and for applying trace elements to mineral-deficient crops are described in U.S. Pat. No. 3,346,494. The use of microemulsions for separating organic compounds in the liquid state is described in U.S. Pat. No. 3,641,181. Oil-in-water microemulsions for lacquers and paints are described in U.S. Pat. No. 4,122,051. A motor fuel in the form of a microemulsion is taught in U.S. Pat. No. 4,046,519.
U.S. Pat. Nos. 3,975,294 and 4,052,331 both describe particular surface-active compositions which can be used as an emulsifier with diorganopolysiloxanes to form transparent microemulsions or transparent gels or to introduce silane cross-linking agents into catalyzed aqueous polysiloxane emulsions to cross-link the emulsion.
Rosano in U.S. Pat. No. 4,146,499 describes a method for the preparation of oil-in-water microemulsions which are described as useful in a variety of applications including as a reaction vehicle for chemical reactions, as a drug delivery system, as an edible food carrier, as a liquid vehicle for water-insoluble dyes and pigments, in cosmetic formulations, and generally for forming stable compositions of hydrophobic substances.
While it is clear that Rosano discloses oil-in-water microemulsions with various ingredients dissolved in the oil phase, this patent does not disclose or suggest dissolving flammable propellants in the oil phase to reduce their flammability.